The present invention relates to a process for the pretreatment of lignocellulosic feedstocks.
Lignocellulosic feedstocks have been proposed as an alternative fuel source for the production of bio-ethanol and other chemicals. Exemplary feedstocks include corn stover, bagasse, switchgrass, pine and poplar. However, these feedstocks typically require pretreatment to overcome their inherent recalcitrance to attack by microorganisms and their enzymes. Existing methods of pretreatment include flow-through pretreatment and steam pretreatment. Flow-through pretreatment includes directing water through a bed of lignocellulosic feedstock. This method optionally includes the addition of mineral acids to promote hydrolysis of the feedstocks into fermentable sugars. Steam pretreatment, by comparison, demonstrates lower material costs over flow-through methods while enhancing the reactivity of the resulting solids.
Despite their advantages, known pretreatment methods involve the partial thermochemical depolymerization and degradation of carbohydrates and lignins in the feedstock. In particular, known flow-through and steam pretreatment methods include sugar losses and yield compounds inhibitory to fermentation. Accordingly, there remains a continued need for an improved pretreatment method to leverage the benefits of lignocellulosic feedstock as a potential fuel source. In addition, there remains a continued need for a system that can retain carbohydrates and lignins at pretreatment conditions while producing a superior concentrate of reactive organics.